The invention relates to extracting energy, and, more particularly, to extracting electrical power from a mechanical disturbance.
A transducer, for example, a piezoelectric transducer, which converts mechanical energy to electrical energy can be used to extract electrical power from a disturbance. It is known to use piezoelectric transducers to extract power from, for example, ocean waves.
A transducer, for example, a piezoelectric transducer, an antiferroelectric transducer, an electrostrictive transducer, a piezomagnetic transducer, a magnetostrictive transducer, or a magnetic shape memory transducer, can be used to convert energy in form of, for example, a mechanical disturbance, to electrical energy. Examples of sources of mechanical energy include: environmental sources such as wind, ocean waves, and earth motion; vibrating machinery such as rotating machinery, compressors, gears, and bearings; human motion such as walking, running, climbing, and hand gestures; human input such as by winding-up a device or shaking a device; vehicle motion such as automobile motion, aircraft motion, and satellite motion; movement of civil structures such as bridges and buildings; acoustic sources such as noise and speech; and impact on or motion of sports equipment.
Electrical power extracted from, for example, human locomotion, can be used to power any device where portable power is needed, for example, personal consumer electronics such as cell phones, pagers, personal organizers, and portable tape players, CD players, and radios. Electrical power extracted from, for example, a vibrating structure such as a tennis racket (or any other sporting equipment), can be used to self-power the transducer and supporting electronics for use of the transducer as a vibration suppression actuator, or to power sensors on the sporting equipment or other special effects. Power extracted from, for example, machinery motion, can be used to self-power the transducer for use as a vibration suppression actuator or to provide power for a remote sensor and wireless telemetry in, for example, condition based maintenance of machinery and structures.
According to one aspect of the invention, a method of extracting power includes coupling a transducer that converts mechanical power to electrical power to a disturbance; coupling an electrical circuit to the transducer such that a peak voltage experienced by the transducer is greater than two times higher than any peak voltage of an open circuit transducer due to the disturbance alone; extracting power from the transducer using the electrical circuit, and storing extracted power.
Embodiments of this aspect of the invention may include one or more of the following features.
The stored extracted power is applied to an external load. Coupling the electrical circuit includes applying stored extracted power to the transducer. Coupling the electrical circuit includes coupling a resonant circuit to the transducer. Coupling the electrical circuit includes controlling switches electrically connected to the transducer. A system state is monitored and the switches are controlled based on the system state. The duty cycle of the switches is controlled.
Coupling the electrical circuit can act to increase oscillations of the disturbance. Alternatively, coupling the electrical circuit can act to dampen oscillations of the disturbance.
In one illustrated embodiment, a plurality of transducers are coupled to the disturbance. Coupling the transducer includes attaching the transducer to a structure.
According to another aspect of the invention, a method of extracting power includes coupling a transducer that converts mechanical power to electrical power to a disturbance; coupling an electrical circuit to the transducer such that a peak of the integral of the current onto and off the transducer is greater than two times higher than any peak of an integral of a current of a short circuit transducer due to the disturbance alone; extracting power from the transducer using the electrical circuit; and storing extracted power.
According to another aspect of the invention, a method of extracting power includes coupling a transducer that converts mechanical power to electrical power to a disturbance; measuring a mechanical state with a sensor, controlling an electrical circuit coupled to the transducer based on the measured system state; extracting power from the transducer using the electrical circuit; and storing extracted power.
According to another aspect of the invention, a method of extracting power includes coupling a transducer that converts mechanical power to electrical power to a disturbance; controlling switches of an electrical circuit coupled to the transducer such that the switches switch at a frequency greater than two times an excitation frequency of the disturbance; extracting power from the transducer using the electrical circuit; and storing extracted power.
According to another aspect of the invention, a method of extracting power includes coupling a transducer that converts mechanical power to electrical power to a mechanical disturbance; extracting power from the transducer and applying power to the transducer during different intervals in the course of the disturbance; and storing extracted power.
Embodiments of this aspect of the invention may include one or more of the following features.
The step of extracting power from the transducer and applying power to the transducer occurs in a single cycle. The step of extracting power from the transducer and applying power to the transducer includes the use of a resonant circuit or amplifier electronics.
According to another aspect of the invention, a system for extracting power includes a transducer that converts mechanical power to electrical power, an electrical circuit, and a storage element for storing extracted power. The transducer is configured for coupling to a disturbance. The electrical circuit is connected across the transducer such that a peak voltage experienced by the transducer is greater than two times higher than any peak voltage of an open circuit transducer due to the disturbance alone.
Embodiments of this aspect of the invention may include one or more of the following features.
The circuit includes a resonant circuit and a rectification circuit. Alternatively, the circuit includes amplifier electronics, for example, arranged as a H-bridge or a half bridge. Control electronics control the amplifier electronics. The control electronics control a duty cycle of the amplifier electronics. The electrical circuit includes a sensor for monitoring a system state.
The storage element is, for example, a capacitor or rechargeable battery. The storage element can include two components connected in series; a side of the transducer is connected to a node between the two components.
According to another aspect of the invention, a system for extracting power includes a transducer that converts mechanical power to electrical power, an electrical circuit, and a storage element for storing extracted power. The transducer is configured for coupling to a disturbance. The electrical circuit is connected across the transducer such that a peak of the integral of the current onto and off the transducer is greater than two times higher than any peak of an integral of a current of a short circuit transducer due to the disturbance alone.
According to another aspect of the invention, a system for extracting power includes a transducer that converts mechanical power to electrical power, an electrical circuit, control logic, and a storage element for storing extracted power. The transducer is configured for coupling to a mechanical disturbance. The electrical circuit includes switching electronics connected across the transducer such that a peak voltage experienced by the transducer is higher than any peak voltage of an open circuit transducer due to the mechanical disturbance alone. The control logic switches the switching electronics at a frequency greater than two times an excitation frequency of the disturbance.
Embodiments of this aspect of the invention may include one or more of the following features.
A sensor measures a system state, and the frequency of switching is based on the measured system state. The control logic controls the switching electronics. The duty cycle of the switching electronics is controlled.
According to another aspect of the invention, a system for extracting power includes a transducer that converts mechanical power to electrical power, an electrical circuit, and a storage element for storing extracted power. The transducer is configured for coupling to a disturbance. The electrical circuit is connected across the transducer and is capable of extracting power from the transducer and applying power to the transducer during different intervals in the course of the disturbance.
According to another aspect of the invention, a method for extracting power includes coupling a transducer that converts mechanical power to electrical power to a disturbance; coupling a resonant circuit to the transducer; and coupling a rectifier to the resonant circuit. Extracted electrical power is used to directly power an external application.
According to another aspect of the invention,a system for extracting power includes a transducer that converts mechanical power to electrical power. The transducer is configured for coupling to a disturbance. A resonant circuit is coupled to the transducer, and a rectifier is coupled to the resonant circuit. Extracted electrical power is used to directly power an external application.
According to another aspect of the invention, a system for extracting power includes a transducer that converts mechanical power to electrical power. The transducer is configured for coupling to a disturbance. A passive voltage doubling rectifier is connected across the transducer. Alternatively, a N-stage parallel fed voltage multiplier is connected across the transducer.